1. Field of the Invention
The present invention concerns a method for operating a magnetic resonance apparatus having a patient positioning table with a tabletop as well as a control device, with which the displacement of the tabletop relative to a homogeneous magnetic field (generated by a magnetic field generation device) and the acquisition of images of an anatomical subject of the patient in a field of view within the homogeneous magnetic field are controlled.
2. Description of the Prior Art
A magnetic resonance apparatus serves for the acquisition of images of a patient that for this purpose is exposed to a homogeneous magnetic field. Radio-frequency magnetic fields, and gradient fields for spatial resolution, are superimposed on this homogeneous magnetic field in order to be able to acquire spatially-resolved resonance signals and generate corresponding images of the examination region therefrom. The basic operation of a magnetic resonance apparatus is well known and need not be described in detail herein.
Because increasingly shorter magnets are used, for the acquisition of anatomical subjects of a patient that are longer than the homogeneous magnetic field or the field of view within the homogeneous magnetic field, the patient lying within the homogeneous magnetic field and within whom the images are acquired, it is typical to move the patient through the magnet (consequently thus to move the homogeneous magnetic field) by suitable table displacement and to acquire the images in various positions, known as levels. The individual various image sets or slice sets that are acquired at the respective table position overlap one another at the edges, such that they can be fused to generate an overall image or a contiguous slice exchange. A typical example is the acquisition of an image of the spinal column that, for example, is approximately 80-90 cm long in adults while the homogeneous magnetic field (known as the homogeneity volume) is typically, maximally approximately 50 cm large while the field of view is sometimes even smaller (depending on the selected measurement sequence), for example only 40 cm with regard to the Z-direction of the magnetic field (corresponding to the movement direction of the patient table).
The user conventionally has to control the table displacement himself or herself, as well as having to define the control parameters. This means that the user had to define the table positions to be acquired, at which table positions the individual slice image stacks are acquired with regard to the length (for example of the spinal column). The user must establish how large the overlap region of the adjoining individual images should be, how large the length of the organ to be acquired, which specific measurement sequence should be selected, dependent on which the field of view possibly changes etc. The user is thus required to employ a number of considerations in order to subsequently, quasi-manually operate the control device. This is laborious and time-consuming; possible errors sometimes lead to incomplete or unusable images.